WesternGun's questions

GNU Bash version 5.1, WSL, Ubuntu 22.04.3 LTS.

$ bash -version
bash -version
GNU bash, version 5.1.16(1)-release (x86_64-pc-linux-gnu)
Copyright (C) 2020 Free Software Foundation, Inc.
License GPLv3+: GNU GPL version 3 or later <http://gnu.org/licenses/gpl.html>

This is free software; you are free to change and redistribute it.
There is NO WARRANTY, to the extent permitted by law.

1. Edit .bashrc, create function foo:

foo() {
    echo 'GHOST'
}

save and exit

2. Source .bashrc:

. .bashrc

Now foo is a valid function:

type foo
foo is a function
foo ()
{
    echo 'GHOST'
}

3. Call foo(), it will print GHOST

4. Edit .bashrc, remove the function, source again

5. foo as a function still available for calling and type.

6. Restart a terminal window, it now stops existing.

7. Of course it also happens when you rename a function; and you keep calling the old version while repeating it pressing UP to use the one in history.

Bug? Feature? Exploit?

I want to update a tar file with part of the content modified, by overwriting the original file, in a script.

I tried tar -u, -A and -r, but none does what I want. I also tried with --overwrite.

An easy test:

cd ~
mkdir test
echo foo > test1.txt
mkdir test_dir
cd test_dir
echo bar > test2.txt
cd ../..
tar cvf test.tar test
tar tvf test.tar # check content
echo barbarbar >> test/test_dir/test2.txt
tar rvf test.jar test # or Avf, or uvf, it's the same: modified file does not overwrite the original file in the tar

• -u --overwrite theoretically will "update", but actually it only appends and does not append the changed file, so I see two test1.txt and one test2.txt there in the tar, with the test2.txt being the old one
• -A --overwrite theoretically will append, but errors out: tar: test: Read error at byte 0, while reading 1024 bytes: Is a directory tar: Error is not recoverable: exiting now
• -r --overwrite theoretically will "append", but will only append, and no overwrite, so I see two test1.txt and two test2.txt in the tar.

I thought: OK then tar does not include the possibility of updating the tar in place. But then I remember that this can be achieved easily by drag the new folder to the tar file in Gnome(I think this is handled by "Archive Manager"), so it's at least possible.

How can I overwrite files in tar in command line/script?

After several frustrations I decided to share it so that next time I don't have to refer to my notebook but Google for it.

Is there some definitive documentation for PS1 strings accepted values?

• escape letters
• colors
• Unicode chars